The present invention relates in general to the production of silicon carbide and more particularly to the continuous production of silicon carbide and other carbide and refractory products utilizing fluidized bed techniques, the apparatus suitable for carrying out such methods, and the novel product resulting therefrom.
In prior art techniques for the commercial production of silicon carbide, large batch-operated furnaces, known as Acheson furnaces, have been provided. In the operation thereof, a high quality silica sand is first mixed with a carbonaceous material, such as petroleum coke, pitch or anthracite to form a charge which is built up around a central core of granular, conductive carbon material, such as calcined petroleum coke or granular graphite. The core is oriented horizontally, and carbon or graphite electrodes are disposed through the end walls of the furnace to make electrical contact with the prepared core. The walls of the furnace comprised loose firebrick, and are usually supported by iron castings which can be removed at the end of the process to facilitate extrication of the treated charge. The temperature in the core generally reaches about 2200.degree. C., and the flow of heat from the core to the surrounding charge causes the carbide formation reaction to take place. Namely: EQU SiO.sub.2 +3C.fwdarw.SiC+2CO.
Although useful for some purposes, certain deficiencies and defects are present in the Acheson process. In many cases, the core temperature becomes too high, and the silicon carbide decomposes to silicon metal and a graphitic form of carbon. Moreover, the energy efficiency of the Acheson process is relatively low--usually less than about 60 percent. Also, periods of 50 to 60 hours or longer are required to complete the charging, heating, and cooling cycle. Yet additionally, the Acheson process is not conducive to containing the influent gases comprising carbon monoxide from the production of silicon carbide.
Wherefore, in view of the deficiencies and defects of prior art techniques, improvement is required and the same is accomplished as is set forth hereinbelow in connection with the description of the novel methods, apparatus and products of the present invention.